Liquid modulator

ABSTRACT

A compression refrigeration system having means to pass the low pressure gas from the evaporator in heat exchange relationship with the high pressure liquid passing from the condenser to the expansion valve. The low pressure gas is passed in heat exchange relationship around the external casing of the receiver/drier, to maintain the receiver/drier at a lower temperature, assist in ensuring that the low pressure gas does not contain any unvaporized liquid, and to cool the high pressure liquid before passage to the expansion valve.

This invention relates to improvements in and relating to automotive airconditioners.

BACKGROUND OF THE INVENTION

Conventional refrigerated automotive air conditioners operate on thehigh pressure system wherein a mechanical compressor compresses therefrigerant which then passes through a condenser where the heat passesfrom the refrigerant to the outside air to thus condense the highpressure gas into a high pressure liquid. After passing through areceiver drier, the high pressure liquid passes then through anexpansion valve to thus pass low pressure liquid through the evaporator,where the low pressure liquid extracts the heat from the air passingover the evaporator to thus cool the air which is then discharged intothe interior of the motor vehicle. The low pressure gas from theevaporator then passes to the compressor where it is again compressedwhereby the heat which is taken up by the evaporation of the liquid intothe gas in the evaporator is then discharged into the ambient air duringthe condensing of the high pressure gas into the high pressure liquidform.

These conventional refrigerated air conditioners have to have a highcapacity in order to adequately cool the heat load of the interior ofthe vehicle, and often this requires that power in the order of 15 horsepower is often required to effectively cool the vehicle.

A great deal of work has been carried out in order to increase theefficiencies of such refrigerated air conditioners, and it has now beenfound that the efficiency of the air conditioner can be effectivelyimproved and thus the power load on the driving motor which is drawn bythe compressor would be greatly reduced.

In this respect it has been found that the refrigerant after passingthrough the evaporator has not been completely vaporized, and the fluidissuing therefrom is a mixture of liquid and vapour. Also the highpressure liquid entering the expansion valve is often at a relativelyhigh temperature, and if the liquid on entry to the expansion valve andalso to the evaporator is of a lower temperature than a greater coolingeffect to the air flowing over the evaporator would take place due tothe fact that more heat has to be extracted from the air in order tovaporize the liquid.

Also with such systems the receiver/drier requires periodic maintenance,and it is common practice to replace the receiver/dryer wheneverrecharging has to be carried out. Also replacement of the unit must takeplace whenever the screens in the receiver/drier become clogged, or whenthe desiccant in the unit is saturated and cannot absorb any moremoisture.

The efficient operation of the receiver/drier depends to a large extentupon its temperature, for the capacity of the desiccant to hold themoisture decreases as its temperature increases.

Hence if the receiver/drier is kept as cool as possible, or is cooled,then its efficiency increases.

BRIEF DESCRIPTION OF THE INVENTION

Thus there is provided according to the invention, means to cool thereceiver/drier, and thus the high pressure liquid to the expansionvalve, and at the same time to ensure that any liquid remaining in thelow pressure gas issuing from the evaporator has been vaporized.

In its simplest form, a casing can be provided around the body of thereceiver/drier, through which casing the low pressure gas from theevaporator is caused to pass, so that the receiver/drier is cooled andthe heat absorbed from the receiver/drier and the high pressure liquidis used to ensure that the low pressure gas is completely vaporized withno droplets of liquid therein.

DESCRIPTION OF THE DRAWINGS

In order to more fully describe the invention reference will now be madeto the accompanying drawings in which:

FIG. 1 is a view of a receiver/drier according to the invention,portions being cut away for clarity,

FIG. 2 is a view of an alternative embodiment,

FIG. 3 is a schematic view of the receiver/drier of the inventionincluded in an automotive air conditioning system,

FIG. 4 is a further alternative of the invention,

FIG. 5 is an exploded view of an alternative form of the invention, and

FIG. 6 is a cross-section thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning firstly to FIG. 3, there is shown an automotive air conditioningsystem including a compressor 1 which passes the high pressure gas tothe condenser 2 where it is condensed into the liquid form, the highpressure liquid passing into the receiver/drier 3. The high pressureliquid then passes through the thermostatic expansion valve 4 where theproper amount of liquid refrigerant is metered into the evaporator 5 asmay be required depending on the heat load. In the evaporator the lowpressure liquid is evaporated into low pressure gas were it is returnedto the compressor.

Conventional systems return the low pressure gas from the evaporator 5to the compressor 1 directly as indicated by the dotted line 6.

However, in accordance with one form of the present invention, the lowpressure gas from the evaporator 5 is not passed directly to thecompressor 1, but is passed through passages 7 to a chamber 8 situatedabout the receiver/drier 3, a passage 9 leading from the chamber 8 tothe inlet of the compressor 1.

It will thus be seen that there is a heat exchange relationship providedat the receiver/drier 3. At times when the heat load on therefrigeration system is greatest, that is in hot weather, that the aircooling the condenser 2 is of high temperature, often up to or evenexceeding 40° C. (104° F.) that the high pressure liquid still is of ahigh temperature and thus contains a considerable amount of heat. Thisheat, if extracted, will result in a lower temperature liquid being fedto the evaporator 5, and will so enhance the cooling effect, for agreater amount of heat will have to be extracted from the air passinginto the vehicle through the evaporator 5. As however, it often occursthat not all the liquid is vaporized in the evaporator 5, the excessheat in the high pressure liquid can be utilized to vaporize this lowpressure liquid.

Thus in accordance with the invention this is accomplished by passingthe high pressure liquid and the low pressure gas in heat exchangerelationship with each other.

In one embodiment this can be carried out in a separate heat exchanger10 as shown in FIG. 4, where the passages 7 and 8, instead of beingconnected to the casing 8 about the receiver/drier 3 as shown in FIG. 3are connected to the heat exchanger 10.

As shown in FIG. 4 the heat transfer through the heat exchanger 10 willreduce the temperature of the high pressure liquid, and also ensure thatall the liquid is vaporized before entering the compressor 1.

However it is preferred to utilize the receiver/drier as a heatexchanger as shown in FIGS. 1 and 2, where the receiver/drier 3 isenclosed in a shell 8, this shell having fittings 11 and 12 for theconnection to the passages 7 and 9. The receiver/drier 3 can be astandard unit, having its inlet and outlet fittings together with thesight glass for the high pressure liquid. While one form ofreceiver/drier 3 is shown it will be appreciated that other forms can beused, with the casing 8 being suitably modified.

As shown the casing 8 is a shell welded to the receiver/drier 3, andthat the heat transfer occurs through the metal casing of thereceiver/drier 3. If desired fins (not shown) can be provided in thecasing 8 to assist in the heat transfer.

Reference to FIG. 2 shows an alternative form where the receiver/drier 3is removable from the outer casing 8, so that the receiver/drier 3 canbe replaced without discarding the casing 8. the casing 8 is in thisembodiment a cylindrical sleeve, and is held in position by end fittingsor caps 13 and 14, which seal on the casing 8 by O-rings or othersealing rings, are held in position by tie bolts 15. The cap 13 hasconnection fittings for the high pressure liquid to pass into thereceiver/drier 3, and also a fitting for the passage of the low pressuregas down the outside of the receiver/drier casing and out an outlet inthe fitting 14.

The end cap 13 has an inlet 16 for the high pressure liquid and anoutlet 17 for the liquid to pass from the receiver/drier, with an outlettube 18 extending into the receiver 3. Suitable desiccant (not shown) isprovided in the receiver 3 between the screens 19.

In this way the receiver/drier 3 can be removed for servicing, or elsecan be serviced and recharged and be returned to the system.

Thus according to the preferred embodiment the receiver/drier 3 isutilized as the heat exchanger, and has the added advantage that theunit is easily fitted, and also the receiver/drier 3 operates at a lowertemperature thus increasing its efficiency.

The casing of the receiver/drier can have fins to extend toward theouter heat exchanger casing, and the end caps can be provided with therespective unions and outlets. The usual sight glass can be fitted inthe end cap in known manner or the sight glass can be provided in theline to the expansion valve.

The desiccant and strainer may thus be replaced in the unit withouthaving to replace the whole unit. The capacity of the unit can be varieddepending on the system and the length of the hoses utilized.

The unit thus in essence comprises two chambers, one for the liquidrefrigerant passing through the filter and desiccant, and the otherchamber containing the suction gas is in heat exchange relationshipstherewith.

A further alternative of the invention is shown in FIGS. 5 and 6.

The liquid modulator 20 is formed as a dismantable unit having end caps21, 22 each provided with a pair of concentric grooves 23, 24 havingsealing rings 25. Cylinders 26, 27 are inserted into the grooves 23, 24and connecting bolts 28 connect the end caps 21, 22 to bolt thecomponent parts together with nuts 29 and washers 30.

There is thus formed a receiver/drier chamber 31 within the cylinder 26and heat exchange chamber 32 within cylinder 27 about the cylinder 26.

End cap 21 is formed with an inlet nipple 33 for passage 34 opening intothe receiver/drier chamber 31 to receive the high pressure liquid fromthe compressor.

The outlet from the chamber 31 is by an outlet tube 35 having anenlarged opening 36 and screen 37 extending downwardly toward the bottomof chamber 31 adjacent end cap 22. The tube 35 is connected to outlettube 38 and nipple 39 in end cap 21 to deliver the high pressure liquidto the expansion valve of the refrigeration system.

A bag D of desiccant is placed in the chamber 31 to absorb moisture inthe system, which bag can readily be replaced as desired. The enlargedinlet to the tube situated adjacent end cap 22 prevents the bag ofdesiccant from blocking the inlet to the tube 35.

End cap 21 also is provided with nipple 40 leading to the inlet passage41 opening into chamber 32 for the low pressure gas from the evaporatorto flow in heat exchange relationship with cylinder 27 and exit throughoutlet passage 42 and nipple 43 in end cap 22.

The liquid modulator unit is thus easily dismantable to allow thedesiccant material to be replaced as desired, it being merely necessaryto remove the nuts 29 one end cap, and remove and replace the desiccantmaterial and then replace the end cap.

Hence there is provided a liquid modulator which is a combined heatexchanger and receiver/drier, the unit thus being easily substitutedinto conventional systems.

I claim:
 1. A receiver/drier for a compression refrigeration systemhaving a compressor, evaporator, condenser and expansion valve, saidreceiver/drier having a hollow body, end caps closing said hollow body,one of said end caps having an inlet and outlet for passage of highpressure liquid therethrough from the condenser to the expansion valve,said outlet having an outlet tube extending through said body toterminate at an end adjacent the other of said end cap, said end of saidtube being expanded to form an inlet covered by a screen, a bag ofdesiccant situated in said body adjacent said outlet tube to absorbmoisture in said liquid, the opening of said enlarged end being closelyspaced from said other end cap to prevent blockage by the desiccant bag,an outer casing surrounding and spaced from said body to form a fluidchamber about said body, an inlet in said one end cap to receive fluidfrom the evaporator to flow into said fluid chamber, an outlet in saidother end cap to deliver fluid to the compressor, whereby high pressurefluid and low pressure gas are in heat exchange relationships throughthe body of the receiver/drier.
 2. A receiver/drier as defined in claim1, characterised in said body and casing being sealed in grooves in saidend caps by clamping bolts bridging said end caps to compress said bodyand casing against sealing rings in said grooves. .Iadd.
 3. Areceiver/drier for a compression refrigeration system having acompressor, evaporator, condenser and expansion valve,saidreceiver/drier being adapted to be connected between said condenser andsaid expansion valve, and comprising a hollow body, end caps closingsaid hollow body, the upper one of said end caps having an inlet forconnection to said condenser to receive liquified refrigerant therefrom,and an outlet for connection to said expansion valve for discharge ofliquified refrigerant thereto for expansion and vaporization in saidevaporator, the lower one of said caps comprising a bottom closurewithout openings, an outlet tube secured in said outlet and extendingthrough said hollow body with an open end adjacent to said lower closedend cap, means supporting a dessicant material inside said hollow bodyin the space around said outlet tube to absorb moisture in the liquidrefrigerant passing therethrough, an outer casing surrounding and sealedto said hollow body in spaced relation thereto to define an annularchamber in heat exchange relation with said hollow body, an inlet in awall of said outer casing for connection to the outlet side of saidevaporator to receive cold, expanded refrigerant fluid therefrom, anoutlet in a wall of said outer casing for connection to the inlet sideof said compressor, whereby hot, high pressure refrigerant liquid andcold, refrigerant gas are conducted in heat exchange relation throughsaid hollow body and said annular chamber, respectively. .Iaddend..Iadd.
 4. A receiver/drier for a compression refrigeration system asdefined in claim 3 in whichsaid end caps are sealed to both said bodyand said outer casing and form the sealed connection therebetween..Iaddend. .Iadd.5. A receiver/drier for a compression refrigerationsystem as defined in claim 3 in which said dessicant supporting meanscomprises a pair of screens positioned laterally in longitudinallyspaced relation in said hollow body and surrounding said outlet tube,and dessicant being supported therebetween. .Iaddend. .Iadd.6. Areceiver/drier for a compression refrigeration system as defined inclaim 3 in which said dessicant supporting means comprises a bag filledwith dessicant and wedged between said outlet tube and the wall of saidhollow body. .Iaddend. .Iadd.7. A receiver/drier for a compressionrefrigeration system as defined in claim 3 in which said end caps aresealed to both said body and said outer casing and form the sealedconnection therebetween, and said dessicant supporting means comprises apair of screens positioned laterally in longitudinally spaced relationin said hollow body and surrounding said outlet tube, and dessicantbeing supported therebetween. .Iaddend. .Iadd.8. A receiver/drier for acompression refrigeration system as defined in claim 3 in which said endcaps are sealed to both said body and said outer casing and form thesealed connection therebetween, and said dessicant supporting meanscomprises a pair of screens positioned laterally in longitudinallyspaced relation in said hollow body and surrounding said outlet tube,and dessicant being supported therebetween. .Iaddend. .Iadd.9. Acompression refrigeration system comprising a compressor, evaporator,condenser and expansion valve, and a receiver/drier connected betweensaid condenser and said expansion valve,said receiver/drier comprising ahollow body, end caps closing said hollow body, the upper one of saidend caps having an inlet connected to said condenser to receiveliquified refrigerant therefrom, and an outlet connected to saidexpansion valve for discharge of liquified refrigerant thereto forexpansion and vaporization in said evaporator, the lower one of saidcaps comprising a bottom end closure without openings, an outlet tubesecured in said outlet and extending through said hollow body with anopen end adjacent to said lower closed end cap, means supporting adessicant material inside said hollow body in the space around saidoutlet tube to absorb moisture in the liquid refrigerant passingtherethrough, an outer casing surrounding and sealed to said hollow bodyin spaced relation thereto to define an annular chamber in heat exchangerelation with said hollow body, an inlet in a wall of said outer casingconnected to the outlet side of said evaporator to receive cold,expanded refrigerant fluid therefrom, and an outlet in a wall of saidouter casing connected to the inlet side of said compressor, wherebyhot, high pressure refrigerant liquid and cold, refrigerant gas areconducted in heat exchange relation through said hollow body and saidannular chamber, respectively. .Iaddend. .Iadd.10. A compressionrefrigeration system including a receiver/drier as defined in claim 9 inwhichsaid end caps are sealed to both said body and said outer casingand form the sealed connection therebetween. .Iaddend. .Iadd.11. Acompression refrigeration system including a receiver/drier as definedin claim 9 in which said dessicant supporting means comprises a pair ofscreens positioned laterally in longitudinally spaced relation in saidhollow body and surrounding said outlet tube, and dessicant beingsupported therebetween. .Iaddend. .Iadd.12. A compression refrigerationsystem including a receiver/drier as defined in claim 9 in which saiddessicant supporting means comprises a bag filled with dessicant andwedged between said outlet tube and the wall of said hollow body..Iaddend. .Iadd.13. A compression refrigeration system including areceiver/drier as defined in claim 9 in which said end caps are sealedto both said body and said outer casing and form the sealed connectiontherebetween, and said dessicant supporting means comprises a pair ofscreens positioned laterally in longitudinally spaced relation in saidhollow body and surrounding said outlet tube, and dessicant beingsupported therebetween. .Iaddend. .Iadd.14. A compression refrigerationsystem including a receiver/drier as defined in claim 9 in which saidend caps are sealed to both said body and said outer casing and form thesealed connection therebetween, and said dessicant supporting meanscomprises a pair of screens positioned laterally in longitudinallyspaced relation in said hollow body and surrounding said outlet tube,and dessicant being supported therebetween. .Iaddend. .Iadd.15. Acompression refrigeration system including a receiver/drier as definedin claim 14 in which said outlet tube has said open end expanded to forman inlet covered by a screen and spaced sufficiently close to said otherend cap to prevent blockage by said dessicant bag. .Iaddend. .Iadd.16. Acompression refrigeration system including a receiver/drier as definedin claim 15 in which said end caps each have concentric grooves withsealing rings therein in which the ends of said body and said casing aresealed, and a plurality of clamping bolts interconnecting said end capsto releasably secure the same in a compressively sealed relation againstsaid sealing rings in said grooves. .Iaddend.